These days, optical disk apparatus (e.g. DVD disk apparatus) that mounts an optical pickup (including an objective lens) for recording a signal onto or reproducing a signal from an optical data record medium (e.g. optical disk such as DVD disk) is now in increasing demand.
These optical disk apparatus have an objective lens driving apparatus for driving an objective lens in response to a control signal and performing focusing control and tracking control.
This invention relates to an objective lens driving apparatus, and particularly to the configuration of a support printed board and its periphery for restraining the ends of windings of a focusing coil or a tracking coil of the objective lens driving apparatus.
An Official Gazette of Japanese Laid-open Public Patent Application Hei 5-342607 describes a conventional objective lens driving apparatus having a support printed board for restraining the ends of windings of a focusing coil or a tracking coil.
The configuration will be explained hereinafter.
FIG. 14(a) shows a front view of the conventional objective lens driving apparatus described in the Official Gazette of Japanese Laid-open Public Patent Application Hei 5-342607.
FIG. 14(b) shows a bottom view of the conventional objective lens driving apparatus described in the Official Gazette of Japanese Laid-open Public Patent Application Hei 5-342607.
FIG. 14(c) shows a left side view of the conventional objective lens driving apparatus described in the Official Gazette of Japanese Laid-open Public Patent Application Hei 5-342607.
In FIG. 14, 1 is an objective lens and 2 is a lens holder to which the objective lens 1 are attached.
A focusing coil 3 for driving the objective lens 1 in the focusing direction (a direction of an arrow shown in FIG. 14, that is, the same direction as that of optical axis of the objective lens 1) and a tracking coil 4 for driving the objective lens 1 in the tracking direction (a direction of an arrow shown in FIG. 14) are wound around the lens holder 2.
Two support printed boards 5 are fixed at two positions indicated by a tip of arrow of the lens holder 2.
The starting ends and the terminating ends of windings of the focusing coil 3 and the tracking coil 4 are restrained by winding a few turns along coil restraining parts, which are located in the vicinity of the front end parts of the support printed boards 5 protruded from the top surface and the bottom surface of the lens holder 2.
6 is a fixed member which is comprised of a printed board and referred to as an act printed board. As shown in the left side view, the act printed board 6 has four patterns, each pattern having a land part and a through hole formed in the center or its periphery of the land part at one end.
7 is a support block which has a recessed part injected with damper material 8 therein and four through holes are formed in said recessed part. The act printed board 6 and the support block 7 are fixed so that four through holes of the act printed board 6 and four through holes of the support block 7, respectively, are placed coaxially.
Each end of four suspension wires 9 made of conductive metal wire is fixed to the act printed board 6 by soldering through the through hole of the act printed board 6 and the through hole of the support block 7 at one end, and is fixed to the coil restraining part of the support printed board 5 by soldering at the other end.
With the above-mentioned configuration, it is possible to obtain a conductive path which starts from one of the patterns of the act printed board 6, through 2 suspension wires 9 connected thereto, a land part of the support printed board 5 connected to the suspension wire 9, the focusing coil 3 connected to the land part of the support printed board 5, other land part of the support printed board 5 connected to other end of the focusing coil 3, other suspension wire 9 connected to the other land part of the support printed board 5, and returns to other one of the patterns of the act printed board 6 connected to the other suspension wire 9.
By feeding current of a focusing control signal to this path, focusing control of the objective lens 1 can be achieved.
Similarly as the focusing control signal, by feeding current of a tracking control signal to the conductive path containing the other two patterns of the act printed board 6, the other two suspension wires 9, the other two land parts of the support printed board 5, and the tracking coil 4, tracking control of the objective lens 1 can be achieved.
Furthermore, the support block 7 is fixed to a yoke 10 at the position as shown in the figure.
The lens holder 2 is supported by four suspension wires 9 so as to be located at the center between permanent magnets 11 and 12.
A magnetic circuit consisting of the permanent magnets 11 and 12, and the yoke 10 provided as an adjunct with the permanent magnets 11 and 12 generates a substantially uniform magnetic field in the vicinity of the focusing coil 3 and the tracking coil 4.
By feeding a focusing control signal to the focusing coil 3 within the uniform magnetic field, Lorentz force is generated, thereby producing a torque for driving the lens holder 2 in the focusing direction.
Likewise, by feeding a tracking control signal to the tracking coil 4 within the uniform magnetic field, Lorentz force is generated, thereby producing a torque for driving the lens holder 2 in the tracking direction.
As four suspension wires 9 are made of flexible metal wire, the lens holder 2 undergoes displacement due to the above-mentioned torque actuation.
Moreover, in the case that windings of the focusing coil 3 and the tracking coil 4 are wound by an automatic winder, parts of the support printed board 5 are configured to protrude from the lens holder 2 and the parts neighboring to the front ends of the protruded support printed board act as coil restraining parts, thereby facilitating restraint of the starting ends and the terminating ends of windings.
The objective lens driving apparatus is required to improve tracking sensitivity for corresponding to high-speed playback. As a solution, it is effective to reduce weight of the movable body.
Specific measures are thinning of the lens holder and weight reduction in the support printed board.
However, weight reduction causes rigidity degradation of the movable body, resulting in the deterioration of high-order resonance characteristic of the objective lens driving apparatus. Although thinning of the lens holder and weight reduction in the support printed board are effective in improving tracking sensitivity, these members become less integrated.
As a result, the coil restraining part of the support printed board which protrudes from the lens holder has a separate vibration mode at high frequencies.
For that reason, with respect to the vibration characteristic of the objective lens driving apparatus, undesired resonance and disturbance in phase occur and tracking performance of the objective lens driving apparatus for the optical data recording medium deteriorates. Further, there is the possibility of consuming electricity unnecessary for tracking.
On the other hand, in order to facilitate the arrangement of the starting ends and the terminating ends of the windings of the coils wound by an automatic winder, it is desirable to configure the coil restraining part of the support printed board to protrude from the lens holder as mentioned above.
An object of the present invention is to provide an inexpensive and easily manufacturable objective lens driving apparatus which is excellent in tracking sensitivity and free from the undesired resonance mode and so on.
Another object of the present invention is to provide an inexpensive manufacturing method for manufacturing an objective lens driving apparatus which is excellent in tracking sensitivity and free from the undesired resonance mode and so on without adding new process.